Common rail fuel injection system and fuel injector for same

Abstract

A fuel injection system is provided which includes a source of high pressure fuel, a low pressure fuel reservoir, and at least one fuel injector which has an injector body that defines a nozzle chamber, a needle control chamber, a needle control vent, a fuel inlet, and a nozzle outlet. A high pressure line extends between the source of high pressure fuel and the fuel inlet. A low pressure line extends between the low pressure fuel reservoir and the needle control vent. A needle control valve is positioned in the injector body and includes a poppet valve member with a first position in which the needle control chamber is fluidly connected to the fuel inlet but closed to the needle control vent. The poppet valve also has a second position in which the needle control chamber is closed to the fuel inlet but open to the needle control vent. A needle valve is positioned in the injector body and includes a one piece needle valve member with a closing hydraulic surface exposed to fluid pressure in the needle control chamber, and an opening hydraulic surface exposed to fluid pressure in the nozzle chamber.

What is claimed is:  
     
       1. A fuel injector comprising: 
       an injector body defining a nozzle chamber, a needle control chamber, a needle control vent, a fuel inlet and a nozzle outlet;  
       a needle control valve positioned in said injector body and including a poppet control valve member having a first position in which said needle control chamber is fluidly connected to said fuel inlet but closed to said needle control vent, and a second position in which said needle control chamber is closed to said fuel inlet but open to said needle control vent;  
       a needle valve member positioned in said injector body and including a closing hydraulic surface exposed to fluid pressure in said needle control chamber and an opening hydraulic surface exposed to fluid pressure in said nozzle chamber;  
       said needle control valve defines a first flow area;  
       a pressure communication passage extending between said needle control valve and said needle control chamber defines a second flow area that is smaller than said first flow area; and  
       said first flow area has a size that is a function of a combined volume of said needle control chamber and said pressure communication passage.  
     
     
       2. The fuel injector of  claim 1  wherein said poppet control valve member is a poppet valve member with an external surface with a first annular valve surface and a second annular valve surface. 
     
     
       3. The fuel injector of  claim 2  wherein said poppet valve member moves a travel distance between said first position and said second position, and said travel distance is less than about 50 microns. 
     
     
       4. The fuel injector of  claim 1  including an electrical actuator positioned in said injector body and being operably coupled to said needle control valve. 
     
     
       5. The fuel injector of  claim 4  wherein said electrical actuator is a solenoid with an armature attached to said poppet control valve member. 
     
     
       6. The fuel injector of  claim 1  wherein said injector body has a centerline; and 
       said needle valve is positioned between said fuel inlet and said nozzle outlet along said centerline.  
     
     
       7. A fuel injector comprising: 
       an injector body defining a nozzle chamber, a needle control chamber, a needle control vent, a fuel inlet and a nozzle outlet;  
       a needle control valve positioned in said injector body and including a poppet control valve member having a first position in which said needle control chamber is fluidly connected to said fuel inlet but closed to said needle control vent, and a second position in which said needle control chamber is closed to said fuel inlet but open to said needle control vent;  
       a needle valve member positioned in said injector body and including a closing hydraulic surface exposed to fluid pressure in said needle control chamber and an opening hydraulic surface exposed to fluid pressure in said nozzle chamber;  
       said injector body defines a pressure communication passage extending between said needle control valve and said needle control chamber; and  
       a combined volume of said pressure communication passage and said needle control chamber is less than about 50 cubic millimeters.  
     
     
       8. A fuel injection system comprising: 
       a source of high pressure fuel;  
       a low pressure fuel reservoir;  
       a plurality of fuel injectors each having an injector body defining a nozzle chamber, a needle control chamber, a needle control vent, a fuel inlet and a nozzle outlet;  
       a high pressure line extending between said source of high pressure said fuel inlet;  
       a low pressure vent line extending between said low pressure fuel reservoir and said needle control vent;  
       a needle control valve positioned in said injector body and including a poppet control valve member having a first position in which said needle control chamber is fluidly connected to said fuel inlet but closed to said needle control vent, and a second position in which said needle control chamber is closed to said fuel inlet but open to said needle control vent;  
       a needle valve positioned in said injector body and including a needle valve member with a closing hydraulic surface exposed to fluid pressure in said needle control chamber and an opening hydraulic surface exposed to fluid pressure in said nozzle chamber;  
       means, including a flow restriction in each fuel injector, for reducing fuel injector performance variations among said plurality of fuel injectors due to geometric variations in said needle control valves of said plurality of fuel injectors;  
       said poppet control valve member is a poppet valve member with an external surface with a first annular valve surface and a second annular valve surface;  
       said needle control valve defines a first flow area;  
       a pressure communication passage extending between said needle control valve and said needle control chamber includes said flow restriction that defines a second flow area that is smaller than said first flow area;  
       an electrical actuator positioned in said injector body and being operably coupled to said needle control valve;  
       wherein said electrical actuator is a solenoid with an armature attached to said poppet control valve member;  
       said injector body has a centerline;  
       said needle valve is positioned between said fuel inlet and said nozzle outlet along said centerline; and  
       said first flow area has a size that is a function of a combined volume of said needle control chamber and said pressure communication passage.  
     
     
       9. A method of fuel injection, comprising the steps of: 
       relieving pressure on a closing hydraulic surface of a needle valve member at least in part by moving a poppet control valve member to a position that closes fluid communication between a common fuel rail and a needle control chamber; and  
       resuming pressure on said closing hydraulic surface at least in part by moving said poppet control valve member to a position that opens fluid communication between said common fuel rail and said needle control chamber; and  
       sizing a flow restriction area in a pressure communication passage extending between said poppet control valve member and said needle control chamber to be more restrictive than a flow area between a seat and said poppet control valve member;  
       sizing a flow restriction area in a pressure communication passage extending between said poppet valve member and said needle control chamber to be more restrictive than a flow area between a seat and said poppet control valve member; and  
       sizing said pressure communication passage and said needle control chamber to have a combined volume less than about 50 cubic millimeters.  
     
     
       10. The method of  claim 9  including a step of setting a travel distance of said poppet valve member to be less than about 50 microns.